U.S. Pat. No. 4,394,409 proposes an elongated wooden structure consisting of four pieces of a sectorial cross-sectional form which, when glued together, form a tubular beam of a square cross-section.
At present, as the numbers of massive tree trunks are decreasing, saw mills are receiving increasing numbers of trunks of a small diameter, from which it is not always possible to produce sawn timber of sufficient size. In the above-mentioned U.S. Pat. No., this is achieved by sawing the wood into pieces of a triangular cross section which are then joined together to produce larger bodies. However, such a structure has the drawback that the wood has to be sawn expressly for this purpose, whereas normally the wood is sawn into pieces of a rectangular cross section.
Previously known are also different tubular structures made of boards joined using various, generally metallic holding means, e.g. nails or angle iron fasteners. However, such structures are difficult and expensive to manufacture industrially, and their strength is generally of a low order.